Acrometastases

Metastases distal to the elbow and the knee (acrometastases) are rare, accounting for approximately 0.1 % of all cases. Acrometastases can appear in patients of every age, with men being twice as likely as women to be affected. The most common primary cancer site is the lung (>50 %), followed by the colon, breast and genito-urinary tract. They mainly appear in cancer patients with wide-spread disseminated disease. Rarely, they may be the first presentation of occult silent cancer, mimicking a benign condition. Current evidence supports that the tumor cells reach the bones of the hands through the circulation and not the lymphatic system; the malignant cells from the lungs have an easy access through the arterial circulation of the arms. The rare incidence of foot acrometastases is believed to be due to the lack of red marrow in these bones, a further distance from the primary cancer site, and the valveless paravertebral venous plexuses (Batson’s plexuses), which allow retrograde tumor cell embolization through the iliofemoral venous system. Treatment depends on staging and tumor extent. Amputative surgery is the more common approach, especially for cancers with poor response to radiation therapy and chemotherapy. In the majority of cases, disarticulation of the ray is required to achieve wide margin resection. In the foot, amputation can be that of a ray, midfoot or transtibial, depending on the location and spread of the tumor. If unresectable, palliative treatment with radiation therapy, bisphosphonates and chemotherapy is recommended. The prognosis of the patients with acrometastatic cancer is poor; the mean survival time after diagnosis is <6 months. An exception seems to be the patients with renal cell carcinoma, if treated with radical surgical resection, and a long latency period between nephrectomy and metastasis has occurred.